<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<style type="text/css">#txt {border:none;font-family:verdana;font-size:16pt;font-weight:bold;border-right-color:#FFFFFF}</style>

<script language="javascript">
var mins;
var secs;
function cd() {
     hour = 1 * h("10");
     mins = 1 * m("10");
     secs = 0 + s(":01");
     redo();
}
function m(obj) {
     for(var i = 0; i < obj.length; i++) {
          if(obj.substring(i, i + 1) == ":")
          break;
     }
     return(obj.substring(0, i));
}
function s(obj) {
     for(var i = 0; i < obj.length; i++) {
          if(obj.substring(i, i + 1) == ":")
          break;
     }
     return(obj.substring(i + 1, obj.length));
}
function dis(mins,secs) {
     var disp;
     if(mins <= 9) {
          disp = " 0";
     } else {
          disp = " ";
     }
     disp += mins + ":";
     if(secs <= 9) {
          disp += "0" + secs;
     } else {
          disp += secs;
     }
     return(disp);
}
function redo() {
     secs--;
     if(secs == -1) {
          secs = 59;
          mins--;
     }
     document.cd.disp.value = dis(mins,secs); // setup additional displays here.
     if((mins == 0) && (secs == 0)) {
          window.alert("Time is up. Press OK to continue."); // change timeout message as required
          // window.location = "yourpage.htm" // redirects to specified page once timer ends and ok button is pressed
     } else {
         cd = setTimeout("redo()",1000);
     }
}
function init() {
  cd();
}
window.onload = init;
</script>
</head>

<body>

<form name="cd">
<input id="txt" readonly="true" type="text" value="10:00" border="0" name="disp">
</form>
</body>
</html>